Theory: He wasn't that rich and he wasn't that successful
His Dad had money but wasn't giving it out to him so easily. He was renting a nice apartment but doesn't own it nor does he own any property.
He doesn't seem to be particularly successful in his job and he's not hard working. This is why he hates Paul - Paul in my opinion is much wealthier, self made wealth. He is hard working, engaging and has made a name for his self around town which is why he's able to get into "Dorcia". Paul is basically on his way to the top, becoming a millionaire.
Patrick can not stand him for this reason. Patrick isn't anything like Paul, he's a guy who's Daddy got him a job and will never be more than his father's son.